Objections to incest

I allow my mind to wander sometimes (particularly on the bus) and somehow wound up thinking about incest. I get that it's wrong, The thought of being sexual with my brother is definitely not appealing, but I don't get why.

What are some objections to incest?

The two I can think of is genetic diversity is compromised in cases of reproduction from incest, and psychologically it may not be healthy.

The genetics argument is essentially invalid due to the availability of contraception, abortions, and the fact that there are over 7 billion people on the planet.

The psychology argument would be valid if shown to be true, although even then it should be treated as a psychological problem, not a criminal one.

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"On the other hand, siblings are very closely related. So they are much more likely to be carriers of the same diseases. And their kids are more likely to get two broken copies of those genes and end up with the disease. But how much more likely?

It turns out that two siblings are 50% related. This means that for any given gene there is a 1 in 4 chance that they have the same copy as each other.

Carriers of recessive genes canpass them on to their children.

Say their dad (but not their mom) is a carrier for a harmful disease such as cystic fibrosis (CF). So dad has one broken copy of CFTR, the CF gene. This means that the brother and sister have a 25% chance of both also being carriers.

If the brother and sister are both carriers and have a child together, then each oftheir children would have a 1 in 4 chance of ending up with CF by getting a disease copy of CFTR from each parent. So the odds of this brother and sister having a child with the disease is (1/4)(1/4) or 1 in 16.

Now imagine that dad is a carrier but that his kids go on to have children with unrelated people. What are the odds that these grandkids will have CF? Around 1 in 240.

We can calculate this number because we know how likely it is for any random person in the U.S. to be a carrier of CF--around 1 in 30. We also know that because dad is a carrier, each of his children has a 1 in 2 chance of getting the disease version of the CFTR gene. So the odds that both parents would be carriers is (1/2)(1/30) or 1 in 60.

The chances that both of these parents would then pass on the disease version of CFTR is the same 1 in 4 that we talked about in our previous example. So the chances are (1/4)(1/60) or 1 in 240.

So the difference between our two examples is 1 in 16 vs. 1 in 240. The siblings are 15 times more likely to have a child with CF than if they had had kids with an unrelated person. The risk becomes more pronounced with more rare diseases."

It's OK to have a relationship but maybe irresponsible genetically to produce offspring.

This gets deep, fast, but we'll probably have to face it when the technology gets cheap enough to show what the actual risks are in parent's genes. I'll bet it'll be reasonable someday to *encourage* abortion in some cases. (Of course that will also apply to non-incest pregnancy.)

But note that the theme that seems to run through the bible, is maintained here as well: the woman is the instigator, the man, blameless!

Of course we're also left with a multitude of unanswered questions:

Why did Lot insist on going to a town, then after a bit there, suddenly decide to live in a cave?

Why would this successful rancher, who had so much livestock that he and his Uncle Abe could no longer even coexist on the same grazing lands, suddenly pack it in to become a possessionless cave-dweller.

In fact, with herds that size, why was he living in a city in the first place? Because it's a necessary gimmick in order to make the story work - logic takes a back seat in this book.

It's very unhealthy psychologically. Humans need to have a range of different types of relationships...platonic, famillial, and romantic...each type helps meet the needs of a person.

On a societal level, isn't it better for people to leave the home and encounter different ways of thinking, living, etc. leading to innovation and cultural development? Incest would seem to promote insular communities.

I agree that it should be treated as a psychological problem, but legal intervention may be necessary if consent cannot be proven and the relationship is harmful.

Going back to the OT, you've got Abraham married to his half-sister, Sarah; their son, Isaac, married to his first cousin, Rebekah; their son, Jacob, married two of his first cousins, Rachel and Leah; and of course there's Lot and his two daughters, rolling around in that cave - think of it as a prequel to "All in the Family."

Before you get anywhere near Abraham, don't we have the incongruity of Adam and Eve and the absence of wives for their sons? I mean Eve must have been a very busy lady with all that begatting to manage...